This proposal seeks support for cross-national comparative analyses of data in a number of existing epidemiologic surveys on patterns, predictors, and consequences of substance use and substance use disorders. All the surveys are based on general population samples and use the recently developed WHO Composite International Diagnostic Interview (CIDI) to assess DSM-III-R substance use disorders. The four surveys to be analyzed in YRS 1-3 include a US national survey, a province-wide survey of Ontario, a survey of Mexicans and Mexican- Americans in California, and a survey of the Mexico City metropolitan area. A total of approximately 25,000 respondents are included in these four surveys. Additional surveys to be added in YRS 4-5 will include all those carried out in general population samples in any country in the world as of the time data analysis begins. This currently includes 18 surveys in 13 countries with a total sample of over 73,000 respondents. Millions of dollars have been and are being invested in these data collections. Yet there is currently no coordinated effort to combine the results into an analysis of world substance use disorders. This is the goal of the current proposal, which aims to: (l) assemble a merged dataset made up from all the above surveys; (2) replicate and expand analyses previously carried out by the PI and his collaborators in the National Comorbidity Survey on patterns and predictors of substance use and substance use disorders; (3) produce data documenting the enormous adverse social consequences of substance use disorders for those who suffer from them and their communities; and (4) export the skills required to carry out these types of analyses to the collaborators in 13 countries around the world. The proposed work is highly significant both for the advancement of our knowledge of the descriptive and analytic epidemiology of substance use disorders and for the social policy goal of increasing international awareness of these disorders as a major public health problem around the world.